The current and pending US EPA and National Highway Traffic Safety Administration (NHTSA) tailpipe emissions and fuel economy standards will require a footprint-based, fleet-average fuel economy of 54.5 MPG for new vehicles by 2025. These impending and aggressive standards provide a significant challenge for the auto industry and have sparked a flurry of discussions among manufacturers and material suppliers to find new solutions to meet these tough federal environmental and fuel efficiency goals.
It is clear today to both auto manufacturers and material suppliers that power train improvements and electrification alone are insufficient in getting the fleet to the 54.5 MPG goal. Vehicles must simultaneously be made lighter; studies have consistently shown that each 10 percent reduction in vehicle curb weight improves fuel economy by six to eight percent. For a typical mid-size passenger car, this means that every 100 pounds removed improves fuel economy by 0.5 to 0.6 MPG. Since the body structure accounts for around one third of a vehicle’s curb weight, body structure light weighting represents the single largest opportunity to improve fuel economy outside of hybridization and electrification.
Thus, the materials race to 54.5 MPG is on. Many in the auto industry speculated that cars of the future would need to be made of an alternative material to achieve the weight reduction needed to meet the new standards. However, new research indicates the auto industry’s venerable material – steel – is one of the more promising solutions for getting auto fleets to 54.5 MPG by the looming deadline.
ArcelorMittal obtained from the US EPA and NHTSA the same, comprehensive computer models used to set and validate their 2012-2025 standards. These models clearly demonstrate that our current and emerging Advanced High Strength Steel (AHSS) grades can deliver not only the light weighting needed to reach 54.5 MPG, but can do so at a lower cost and with less environmental impact than alternative materials.
The models show that the weight reduction offered by AHSS provides not only one of the largest improvements in fuel economy, but also the single most cost-effective improvement in terms of improvement per dollar spent, of any known fuel economy improvement technology. AHSS can provide a 7.2 percent fuel economy improvement at little or no additional cost to the auto manufacturer - up to six times more cost-effective than aluminum. Additionally, fleets made from these advanced steel grades can also be produced using auto manufacturers’ existing infrastructure with little to no need for additional investments in retooling auto production facilities.
But that’s not the end of it. Knowing the EPA’s ultimate goal is to reduce greenhouse gas emissions, it’s essential to take into account Total Life Cycle Analysis (LCA) to assure that technologies used to reduce use-phase tailpipe emissions do not inadvertently increase a vehicle’s overall total life cycle carbon footprint. Producing aluminum releases five times more CO2 to the environment compared to producing AHSS. Producing carbon fiber releases ten times more CO2 compared to AHSS. Cars made of these other materials can have an as-manufactured carbon footprint over twice that of a car made of AHSS. Cars made of all three of these materials can achieve the 54.5 MPG goal. With no use phase tailpipe emission advantage among the three, the cars made of AHSS will have the lower overall LCA carbon footprint.
Steel also has the unique advantages of being infinitely recyclable and the ability to be recycled interchangeably between end-use applications without compromising its inherent properties. Steel’s unique magnetic properties allow it to be easily separated from other materials in the recycling stream. As a result, virtually 100 percent of the steel from scrapped cars is recycled, dramatically reducing the carbon emissions from making new cars. The alternative materials will have an extremely difficult challenge in approaching steel’s recycling rate.
When U.S. EPA and NHTSA first announced the new 2025 CAFE standards, proponents of competing alternative materials proclaimed that it was “game over” for steel. But, a close look at the facts and new data show that depiction couldn’t be farther from the truth. Steel can get the 2025 fleet to 54.5 and can do so at lowest cost and lowest total life cycle carbon footprint. With aggressive new fuel efficiency targets on the horizon, steel’s esteemed role as the foundation of the automobile is on track to be every bit as relevant and essential in 2025 as it is today.
Blake Zuidema is the Director of Automotive Product Applications for ArcelorMittal, the world's leading steel and mining company. For the sixth consecutive year, ArcelorMittal USA is the only steelmaker to be honored as an ENERGY STAR Partner of the Year by the US Environmental Protection Agency and the US Department of Energy.
